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04 Multiple Choice

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4)A ball of mass 1.2 kg is dropped from a height of 30 m. As it falls, 25% of its initial gravitational potential energy is
transferred to thermal energy. What is the kinetic energy of the ball just before it hits the ground?

1 Answer

5 votes
Eg = mgh = (1.2 kg) ( 9.81 N/kg) (30m)
Eg = 353.16 J

Eh = Eg * 0.25
Eh = (353.16 J) (0.25)
Eh = 88.29 J

Ek = Eg - Eh
Ek = (353.16 J) - (88.29)
Ek = 264.87 J

Therefore the kinetic energy just before the ball hits the floor is 264.87 J
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